US8593998B2 - Time reversal method of processing symbols in bidirectional communication - Google Patents

Time reversal method of processing symbols in bidirectional communication Download PDF

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US8593998B2
US8593998B2 US12/529,928 US52992808A US8593998B2 US 8593998 B2 US8593998 B2 US 8593998B2 US 52992808 A US52992808 A US 52992808A US 8593998 B2 US8593998 B2 US 8593998B2
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entity
pulse
transmitted
guard interval
symbols
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US20100085902A1 (en
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Dinh Thuy Phan Huy
Jean-Marie Chaufray
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3G Licensing SA
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France Telecom SA
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0212—Channel estimation of impulse response
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
    • H04L25/03114—Arrangements for removing intersymbol interference operating in the time domain non-adaptive, i.e. not adjustable, manually adjustable, or adjustable only during the reception of special signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03343—Arrangements at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
    • H04L27/2607—Cyclic extensions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L2025/03777—Arrangements for removing intersymbol interference characterised by the signalling
    • H04L2025/03802—Signalling on the reverse channel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT

Definitions

  • the present invention relates to processing symbols transmitted in a time-division duplexing (TDD) radiocommunications network using orthogonal frequency-division multiplex (OFDM) modulation, for example.
  • TDD time-division duplexing
  • OFDM orthogonal frequency-division multiplex
  • It relates more particularly to introducing the time reversal technique into such systems for communication in the uplink and downlink directions.
  • Time reversal is a technique for focusing waves, typically acoustic waves, that relies on the invariance of the wave equation on time reversal.
  • a short pulse transmitted from a source point propagates in an unknown propagation medium.
  • a portion of this wave is picked up, generally by a set of sensors known as a time reversal mirror (TRM), digitized, and time reversed before being sent back in the propagation medium.
  • TRM time reversal mirror
  • the wave then retraces its previous steps and converges toward the source point, where it forms a short pulse.
  • the signal collected at the source point is in a form virtually identical to that of the original signal transmitted from the source point.
  • the more complex the propagation medium the more accurately the reversed wave converges toward the source point.
  • time reversal technique can be extended to radiocommunications networks to improve the equalization of the propagation channels and thus the processing of symbols received via those propagation channels.
  • using time reversal requires the transmitter to have knowledge about the propagation channels.
  • time duplexing uses the time reversal technique to improve the quality of service both in the uplink direction and in the downlink direction without recourse to additional network resources.
  • a method of the invention for processing symbols separated by guard intervals and transmitted in frames via a propagation channel between first and second communicating entities using time-division duplexing is characterized in that it includes, in the second entity:
  • the second entity transmitting a pulse during the predetermined guard interval of the frame, whilst preserving the duration of the frame, enables the first entity to determine the propagation conditions of the channel before transmitting a frame. No additional time resource is therefore reserved specifically for estimating the impulse response of the propagation channel as a function of the pulse received in the frame.
  • each guard interval is assigned to transmitting redundancy data
  • the redundancy data relating to the predetermined guard interval is replaced by the pulse to be transmitted or the size of the redundancy data is reduced in the predetermined guard interval to transmit a pulse therein.
  • the size of at least the redundancy data in the frame is reduced, guard intervals including the reduced-size redundancy data are made smaller, and the predetermined guard interval is created with a duration corresponding to the reduction in the size of the guard intervals.
  • Time reversal is therefore used with minimum impact on the frame structure, since the frame duration is unchanged and only the redundancy data relating to a guard interval is liable to be modified.
  • the pulse can be transmitted during the last guard interval of the frame, in order for the entity receiving the pulse to determine a recent state of the propagation channel.
  • the second entity can comprise a plurality of antennas and transmit as many second pulses at different times during the frame as the second entity has antennas.
  • the use in accordance with the invention of the time reversal technique is therefore adapted to systems with a plurality of transmit antennas and a plurality of receive antennas guaranteeing a high transmission bit rate in the uplink and downlink directions.
  • the pulse is transmitted in analog form during the predetermined guard interval of the frame.
  • An impulse response of the propagation channel is then estimated as a function of the pulse received by the first entity and is used to filter a signal comprising the symbols of another frame as a function of the time-reversed impulse response.
  • the pulse is transmitted in the form of a bit sequence during the predetermined guard interval of the frame.
  • An impulse response of the propagation channel is then estimated as a function of said bit sequence received by the first entity on the basis of a discrete model of the propagation channel and time reverses the estimated impulse response to filter symbols to be transmitted.
  • the invention also relates to a communicating entity for processing symbols separated by guard intervals and transmitted in frames via a propagation channel between said communicating entity and another communicating entity using time-division duplexing, characterized in that it includes:
  • the invention relates to a computer program adapted to be executed in a communicating unit to process symbols transmitted in frames using time-division duplexing, said program including instructions that execute the steps of the method of the invention when the program is executed in said communicating entity.
  • FIG. 1 is a block diagram of two entities communicating via a radiocommunications network
  • FIG. 2 is a block diagram of a communicating entity of the invention
  • FIG. 3 shows an algorithm of a symbol processing method of the invention
  • FIGS. 4A and 4B show a frame of symbols conforming to variants of a first implementation of the invention.
  • FIG. 5 shows a frame of symbols conforming to a second implementation of the invention.
  • first and second communicating entities EC 1 and EC 2 are adapted to communicate via a radiocommunications network RR.
  • the radio communications network RR is a cellular digital radio communications network, for example of the GSM (Global System for Mobile communications) or UMTS (Universal Mobile Telecommunications System) type, or a Wireless Local Area Network (WLAN) or a WIMAX (Worldwide Interoperability Microwave Access) network.
  • GSM Global System for Mobile communications
  • UMTS Universal Mobile Telecommunications System
  • WLAN Wireless Local Area Network
  • WIMAX Worldwide Interoperability Microwave Access
  • the radiocommunications network RR is an ad hoc wireless local area network having no infrastructure.
  • the two communicating entities are two terminals that communicate directly and spontaneously without the intermediary of communication centralization equipment such as an access terminal or point or a base station.
  • the two communicating entities utilize a propagation channel for time-division duplex transmission of signals.
  • the propagation channel in a first direction for example the downlink direction from the entity EC 1 to the entity EC 2
  • the propagation channel in a second direction opposite the first direction i.e. the uplink direction from the entity EC 2 to the entity EC 1 .
  • Communication between a base station and a mobile radio terminal is effected at different times for transmission and reception on the same carrier frequency.
  • the base station (entity EC 1 ) transmits on the downlink channel a signal that is received and processed by the mobile terminal (entity EC 2 ) and during a second time slot the mobile terminal transmits on the uplink channel a signal that is received and processed by the base station.
  • Each entity EC 1 , EC 2 transmits a signal during a radio frame TR containing time slots IT dedicated to transmitting symbols SB and separated by guard intervals IG.
  • the symbols carried by a signal transmitted over the propagation channel are subject to multipath echoes.
  • a symbol SB transmitted by the first entity EC 1 is received by the second entity EC 2 in the form of a plurality of symbols attenuated and delayed differently. Consequently, a symbol transmitted during a given time slot IT can be at least partly superposed on an echo relating to the symbol transmitted during a time slot following the given time slot. Interference then occurs between the symbols. To prevent this interference, a guard interval IG of duration d is added between times slot IT of duration is occupied by a transmitted symbol.
  • the symbol portion transmitted during the guard interval IG is typically referred as the “cyclic prefix”.
  • each communicating entity EC 1 , EC 2 includes an antenna corresponding to a propagation channel between the two single input-single output (SISO) communicating entities EC 1 and EC 2 .
  • each communicating entity EC 1 , EC 2 comprises a plurality of antennas corresponding to propagation channels between the two multiple input-multiple output (MIMO) communicating entities EC 1 and EC 2 .
  • MIMO multiple input-multiple output
  • FIG. 2 shows only the means relating to the invention included in one of the two communicating entities.
  • the two communicating entities comprise similar means since the principle of communication between the two entities is the same in the downlink direction and in the uplink direction.
  • Those means comprise a modulator MOD, a pulse generator GI, a pulse analyzer AI, and a demodulator DEM.
  • Each entity further comprises at least one transmit/receive antenna ANT that can consist of a plurality of antennas.
  • the modulator MOD converts a sequence of bits into complex symbols that are transmitted in the form of a block of symbols during a radio frame TR containing time slots IT each dedicated to transmitting a symbol SB. As described above, two consecutive time slots in each frame are separated by a guard interval IG during which either no signal is transmitted or redundancy data DR is transmitted.
  • the block of symbols transmitted during a frame contains 68 OFDM symbols separated from each other by redundancy data that consists of cyclic prefixes, for example.
  • a pulse is transmitted from a source point, propagates in an unknown propagation medium, and is received and processed at a reception point.
  • the received wave is then digitized and time reversed before being transmitted back into the propagation medium in order to converge toward the source point, where it forms a pulse.
  • the pulse IMP can be processed in analog or digital form.
  • the pulse generator GI generates a pulse IMP that is transmitted during one or a few of the guard intervals IG of a radio frame TR of symbols to be transmitted.
  • the pulse generator GI cooperates with the modulator MOD to transmit the pulse IMP only during a predetermined guard interval that is not dedicated to transmitting redundancy data, so that only the pulse transmitted for each radio frame TR by the transmit antenna is received without interference via the propagation channel by the receive antenna of the other communicating entity.
  • the transmit and receive antennas of an entity can be combined in a single antenna ANT connected to a circulator.
  • the pulse of the transmitted radio frame TR is received by the receive antenna ANT of the other communicating entity and then processed directly by the pulse analyzer AI, which stores the impulse response RI of the propagation channel.
  • the pulse analyzer AI time reverses the impulse response and forwards it to the modulator MOD, which in turn filters the symbols to be transmitted as a function of the time-reversed impulse response.
  • the pulse generator GI commands the modulator MOD to insert a bit sequence, which can comprise only one bit at “1”, during one or a few of the guard intervals IG of a radio frame TR of symbols to be transmitted.
  • said guard interval contains two series of bits at “0” separated by one bit at “1”. Transmitting this bit sequence is then considered as transmitting a pulse IMP after analog conversion of the digital signal at the output of the pulse generator.
  • the symbols received by the receive antenna ANT of the other communicating entity during the radio frame TR are applied to amplification, frequency demodulation, and tuned filtering stages at the input of the demodulator DEM.
  • the bits corresponding to the demodulated received pulse are then forwarded to the pulse analyzer AI which estimates the impulse response of the channel and time reverses it to form the transfer function of a pre-distortion digital filter FD to be forwarded to the modulator MOD, which uses the pre-distortion filter FD to filter the symbols of the next radio frame to be transmitted and then modulates the filtered symbols before transmitting them.
  • the modulator MOD processes the symbols to be transmitted as a function of the received pulse and transmits another pulse in the frame of symbols to be transmitted.
  • the signal transmitted by one of the entities and deformed as a function of the received pulse is then received by the other of the entities in a form similar to the form that the signal would have had if it had not been processed as a function of the received pulse, which is known as time reversal processing.
  • time reversal processing By means of the time reversal technique, the transmitted signal converges toward the source point of the pulse, which reduces the dispersion of the propagation channel and improves the processing of the symbols received.
  • the transmission method of the invention comprises steps E 1 to E 6 executed automatically in the two communicating entities.
  • steps E 1 to E 3 and E 6 are described in relation to a first communicating entity EC 1 and the steps E 4 and E 5 are described in relation to a second communicating entity EC 2 . Because the two entities communicate bidirectionally using time-division duplexing, the steps E 1 to E 3 and E 6 and the steps E 4 and E 5 can also be executed in the second entity EC 2 and the first entity EC 1 , respectively.
  • the modulator MOD of the first communicating entity EC 1 converts a sequence of bits into symbols SB that are to be transmitted in the form of a block of symbols during a first radio frame TR 1 containing time slots IT each of which is dedicated to transmitting a symbol SB and that are separated by guard intervals IG dedicated to transmitting redundancy data DR, for example.
  • the first communicating entity EC 1 generates a pulse IMP to be transmitted during a predetermined guard interval IGp of the first radio frame TR 1 .
  • the step E 2 is either an analog processing step E 21 or a digital processing step E 22 .
  • the pulse generator GI cooperates with the modulator MOD to generate a pulse IMP that must be transmitted during a predetermined guard interval IGp of the first radio frame TR 1 of symbols to be transmitted.
  • the pulse is for example mixed with the first frame TR 1 during the guard interval IGp under the control of the pulse generator GI.
  • the pulse generator GI commands the modulator MOD to insert a predetermined bit sequence into a predetermined guard interval IGp of the first radio frame TR 1 of symbols to be transmitted.
  • the transmitted bit sequence takes the form of a pulse IMP after analog conversion of the predetermined bit sequence.
  • the predetermined guard interval IGp is assigned to transmitting redundancy data DR.
  • the pulse IMP is transmitted in place of said redundancy data DR, which is erased and is not transmitted in the guard interval IGp.
  • the size of the redundancy data DR is reduced to a predefined size thereby releasing a duration available for transmitting the pulse IMP in the predetermined guard interval IGp.
  • the pulse is transmitted before or after the reduced redundancy data. In this first implementation, the total duration tt for each symbol transmitted is unchanged.
  • the pulse IMP is transmitted during the final guard interval IG of the radio frame TR 1 in order for the second entity EC 2 to analyze as recent as possible an impulse response of the propagation channel for each frame period.
  • guard intervals are not dedicated to transmitting redundancy data DR and the pulse IMP is transmitted during a predetermined guard interval IGp, for example the final one of the first frame TR 1 , without modifying the original data to be transmitted.
  • some or all of the redundancy data DR of a radio frame TR 1 c transmitted by the entity EC 1 has a predefined reduced size relative to the size of the standard redundancy data and consequently the guard intervals IG including the reduced redundancy data are smaller.
  • the guard intervals IG including the reduced redundancy data are smaller.
  • the guard intervals IG including the reduced redundancy data are released at the end of the frame TR 1 c at the end of the frame TR 1 c there is released a duration corresponding to the reduction in the size of the guard intervals IG including the reduced redundancy data, which creates a guard interval for transmitting the pulse IMP.
  • the time reversal technique explained above reduces the dispersion of the propagation channel and therefore the echoes of the symbols received. Consequently, the redundancy data, which generally has a size able to cover at least all the delays relative to the echoes of the symbols, can be reduced in proportion to the reduction of the dispersion of the propagation channel.
  • the redundancy data DR is considered to be divided into 30 samples, for example. Using time reversal reduces the size of the redundancy data by at least one sample. If a radio frame TR 1 c contains more than 30 symbols SB, and thus more than 30 items of redundancy data DR, at least 30 time units each relating to one redundancy data sample are released. The 30 time units are grouped together at the end of the frame to create a predetermined guard interval IGp that preserves the total duration of the frame. In this second implementation, the guard intervals IG have a duration d′ that is reduced relative to the standard deviation d of the guard intervals.
  • the total intended duration tt′ for each symbol transmitted is also reduced relative to the standard total duration tt of the symbols.
  • the duration of the pulse IMP in the predetermined guard interval IGp is n ⁇ (d ⁇ d′).
  • the first entity EC 1 transmits the first frame TR 1 and the pulse IMP during the predetermined guard interval IGp of the frame TR 1 to the second entity EC 2 via the propagation channel between the transmit antenna of the first entity EC 1 and the receive antenna of the second entity EC 2 .
  • the second entity EC 2 estimates an impulse response of the propagation channel as a function of the received pulse and time reverses the estimated impulse response.
  • the time-reversed impulse response is used for dynamic construction of a digital filter to be applied by the second entity EC 2 to symbols to be transmitted.
  • the pulse analyzer AI of the second entity EC 2 directly stores the impulse response RI of the propagation channel as a function of the pulse received.
  • the pulse analyzer AI time reverses the impulse response.
  • the pulse analyzer AI stores the coefficients of the impulse response RI and classifies the conjugates thereof in an order that is the reverse of that of the coefficients of the impulse response, for example. These coefficients are then those of the time-reversed impulse response and are used for the dynamic construction of a pre-distortion digital filter FD for filtering the symbols to be transmitted.
  • the pulse analyzer AI forwards the filter FD to the modulator MOD.
  • the pulse analyzer AI analyzes the impulse response RI of the propagation channel as a function of the pulse received by an analog splitter under the control of the pulse analyzer and deduces from it a discrete model of the propagation channel.
  • the pulse analyzer AI then time reverses the discrete model of the channel to form a pre-distortion filter FD that is forwarded to the modulator MOD in order for the pre-distortion filter to filter the symbols to be transmitted.
  • the second entity EC 2 uses the pre-distortion filter to filter symbols to be transmitted to the first entity EC 1 as a function of the time-reversed impulse response.
  • the second entity EC 2 then transmits to the first entity EC 1 a second frame TR 2 containing the symbols filtered as a function of the time-reversed impulse response after the step E 4 .
  • the second entity EC 2 transmits a pulse IMP in analog or digital form during a predetermined guard interval IGp of the second frame TR 2 . Accordingly, the first entity EC 1 processes the pulse contained in the second frame TR 2 in the same manner as in the step E 4 .
  • the first entity EC 1 receives the second frame TR 2 .
  • the time reversal technique reduces the time dispersion of the propagation channel.
  • the demodulator DEM of the first entity equalizes and then recovers the symbols of the second frame more simply and more quickly than in the prior art technique, since the signal corresponding to the frame received is “pre-equalized” in the entity EC 2 when transmitted, i.e. the received signal contains few echoes and is similar in amplitude and frequency to the signal that was initially applied to the modulator MOD before time-reversal processing of the symbols.
  • processing effected in the step E 6 is also effected by each entity on receiving a frame.
  • the symbols of a frame are processed as and when the frame is received.
  • each entity EC 1 , EC 2 functions in spatial diversity mode and comprises a plurality of transmit/receive antennas.
  • a pulse is specific to the propagation channel between a transmit antenna of the first entity EC 1 and a receive antenna of the second entity EC 2 . If the first entity EC 1 comprises AN 1 antennas and the second entity EC 2 comprises AN 2 antennas, then there are AN 1 ⁇ AN 2 propagation channels between the two entities, the numbers AN 1 and AN 2 being integers that are different or equal.
  • the first entity EC 1 transmits AN 1 separate pulses at different times during a first frame TR 1 via the respective AN 1 transmit antennas.
  • the second entity EC 2 during the second frame TR 2 , at least AN 2 separate pulses must be transmitted at respective different times by the AN 2 transmit antennas.
  • AN 1 pulses are respectively transmitted during the last AN 1 guard intervals IG of the first frame TR 1 a or TR 1 b.
  • AN 1 pulses are transmitted successively at the end of the first frame TR 1 c during a guard interval duration created by the reduction of the guard intervals IG, for example.
  • the pulse analyzer AI estimates the impulse response of the propagation channels between an antenna of the first entity by which the pulse was transmitted and the various antennas of the second entity. For each pulse received, the pulse analyzer therefore estimates AN 2 impulse responses and after receiving all of the first frame TR 1 the pulse analyzer has estimated AN 1 ⁇ AN 2 impulse responses.
  • the second entity EC 2 time reverses the AN 1 ⁇ AN 2 estimated pulse responses and combines them to form a single pre-distortion digital filter FD. For example, the coefficients of the same rank of each reversed impulse response are weighted and summed to obtain a coefficient of the pre-distortion filter FD.
  • the second entity EC 2 then filters symbols as a function of the pre-distortion filter FD and transmits the filtered symbols to the first entity EC 1 , which receives them on each of the AN 1 antennas.
  • one of the two entities in fact consists of a plurality of entities.
  • the second entity EC 2 consists of N second entities EC 21 to EC 2 N, with N ⁇ 2.
  • Each second entity EC 2 n with 1 ⁇ n ⁇ N, comprises AN 2 n antennas and the first entity EC 1 comprises AN 1 antennas.
  • the first entity EC 1 transmits AN 1 separate pulses at different times during a first frame TR 1 via the respective AN 1 transmit antennas.
  • each second entity EC 2 n during the second frame TR 2 , at least AN 2 n separate pulses must be transmitted at different times by the respective AN 2 n transmit antennas.
  • respective commands to transmit the pulses are transmitted to the N second entities in signaling messages from the first entity EC 1 .
  • each second entity EC 2 n estimates AN 2 n impulse responses and after receiving the whole of the first frame TR 1 the pulse analyzer has estimated AN 1 ⁇ AN 2 n impulse responses.
  • Each second entity EC 2 n time reverses the AN 1 ⁇ AN 2 n estimated pulse responses and combines them to construct dynamically a single pre-distortion digital filter FDn.
  • Each second entity EC 2 then filters symbols using the filter FDn and transmits the filtered symbols to the first entity EC 1 .
  • the invention described here relates to a method and a communicating entity for processing symbols transmitted in frames using time-division duplexing.
  • the steps of the method of the invention are determined by the instructions of a computer program incorporated in the communicating entity.
  • the program includes program instructions which execute the steps of the method of the invention when said program is executed in a processor of the communicating entity the operation of which is then controlled by the execution of the program.
  • the invention also applies to a computer program, notably a computer program stored on or in a storage medium readable by computer or any other data processing device, adapted to implement the invention.
  • This program can use any programming language and take the form of source code, object code or a code intermediate between source code and object code such as a partially compiled form or any other form desirable for implementing the method of the invention.
  • the storage medium can be any entity or device capable of storing the program.
  • the medium can include storage means in which the computer program of the invention is stored, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a USB key, or magnetic storage means, for example a floppy disk or a hard disk.
  • the storage medium can be a transmissible medium such as an electrical or optical signal, which can be routed via an electrical or optical cable, by radio or by other means.
  • the program of the invention can in particular be downloaded over an Internet-type network.
  • the storage medium can be an integrated circuit incorporating the program and adapted to execute the method of the invention or to be used in its execution.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Bidirectional Digital Transmission (AREA)
US12/529,928 2007-03-05 2008-02-07 Time reversal method of processing symbols in bidirectional communication Active 2029-10-17 US8593998B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR0753651A FR2913555A1 (fr) 2007-03-05 2007-03-05 Traitement de symboles dans une communication bidirectionnelle par retournement temporel.
FR0753651 2007-03-05
PCT/FR2008/050187 WO2008110722A2 (fr) 2007-03-05 2008-02-07 Procede de traitement de symboles dans une communication bidirectionnelle par retournement temporel, et entite communicante pour sa mise en oeuvre

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US20100085902A1 US20100085902A1 (en) 2010-04-08
US8593998B2 true US8593998B2 (en) 2013-11-26

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US9407306B2 (en) 2014-04-25 2016-08-02 Origin Wireless, Inc. Quadrature amplitude modulation for time-reversal systems
US9559874B2 (en) 2013-08-16 2017-01-31 Origin Wireless, Inc. Multiuser time-reversal division multiple access uplink system with parallel interference cancellation
US9686054B2 (en) 2014-07-17 2017-06-20 Origin Wireless, Inc. Joint waveform design and interference pre-cancellation for time-reversal systems
US9883511B1 (en) 2012-12-05 2018-01-30 Origin Wireless, Inc. Waveform design for time-reversal systems
US9882675B2 (en) 2013-08-16 2018-01-30 Origin Wireless, Inc. Time-reversal wireless systems having asymmetric architecture
US9887864B1 (en) 2014-03-10 2018-02-06 Origin Wireless, Inc. Methods, devices and systems of heterogeneous time-reversal paradigm enabling direct connectivity in internet of things
US10009148B1 (en) 2015-01-22 2018-06-26 Origin Wireless, Inc. Time-reversal technologies for hybrid wireless networks
US10122409B2 (en) 2012-12-03 2018-11-06 University Of Maryland At College Park Systems and methods for time-reversal division multiple access wireless broadband communications
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US20100085902A1 (en) 2010-04-08
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FR2913555A1 (fr) 2008-09-12
WO2008110722A2 (fr) 2008-09-18
CN101627594A (zh) 2010-01-13
EP2115980A2 (fr) 2009-11-11

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